Heat-insulation film for high temperature molding, vacuum thermal insulator using same and process for fabricating vacuum thermal insulator

ABSTRACT

Disclosed are a heat-insulation film laminated with formability at a high temperature, a vacuum thermal insulator covered on an outer portion of a core material of the heat-insulation film, and a method of fabricating the vacuum thermal insulator in which the heat-insulation film is covered on the outer portion of the core material through the thermal-fusion process. The heat-insulation film is stably covered on the outer portion of the core material through the thermal-fusion process at the high temperature.

TECHNICAL FIELD

The present invention relates to a heat-insulation film. Morespecifically, the present invention relates to a heat-insulation filmthat can be thermal-fusion formed, a vacuum thermal insulator includingthe heat-insulation film, and a method of fabricating the vacuum thermalinsulator through the thermal-fusion process using the heat-insulationfilm.

BACKGROUND ART

Recently, a vacuum thermal insulator has been extensively used insteadof a conventional thermal insulator, such as polyurethane or styrofoam.Generally, the vacuum thermal insulator has a structure in which anouter portion of a core material is surrounded by a heat-insulation filmrepresenting low transmittance similar to that of gas or moisture andserving as an outer skin material. Since the vacuum thermal insulatorrepresents a significantly excellent thermal insulation effect, thedemand for the vacuum thermal insulator is recently increased.

The heat-insulation film generally used as the outer skin material ofthe vacuum thermal insulator has a structure in which films arelaminated at several layers. Especially, the heat-insulation film has alamination structure of complex plastic representing an excellent gasbarrier property. A vacuum thermal insulator according to the relatedart is fabricated by receiving plastic foam or an inorganic material asa core material, decompressing an internal structure, and sealing anouter portion of the core material using the heat-insulation filmthrough a high-frequency scheme. However, when the heat-insulation filmis bonded to the outer portion of the core material through a vacuumhigh-frequency scheme, the heat-insulation film may not tightly makecontact with the core material from, especially an edge portion of thecore material in the process of covering the outer portion of the corematerial with the heat-insulation film. Accordingly, air or moisturepasses through the heat-insulation film, so that the degree of vacuum islowered according to the elapse of time. Accordingly, the insulatingproperty of the heat-insulation film may not be maintained. Especially,the heat-insulation film may be deformed at high humidity.

In addition, when forming the surface and the edge portion of the corematerial in the process of sealing the heat-insulation film tomanufacture the vacuum thermal insulator according to the related art,the heat-insulation film may be twisted, so that produce failure mayoccur.

DISCLOSURE Technical Problem

The present invention is suggested to solve the problem of the relatedart, and an object of the present invention is to provide aheat-insulation film having excellent heat resistance and a vacuumthermal insulator having the heat-insulation film as an outer skinmaterial thereof.

Another object of the present invention is to provide a method offabricating a vacuum thermal insulator capable of facilitatingprocessing and forming works by covering an outer portion of a corematerial with a heat-insulation film having excellent heat resistancethrough a thermal-fusion molding process.

Technical Solution

In order to accomplish the above object of the present invention, thereis provided a heat-insulation film including a first film layerincluding a material selected from the group consisting of polyethyleneterephthalate (PET), polyethylene naphthalate (PEN), and polyimide (PI),a first barrier layer laminated on one surface of the first film layerthrough a first bonding layer including a material selected from thegroup consisting of linear low density polyethylene (LLDPE), low densitypolyethylene (LDPE), high density polyethylene (HDPE), castedpolypropylene (CPP), polyethylene, polyethylene terephthalate (PET),polypropylene (PP), ethylene vinyl acetate (EVA), epoxy resin, andphenol resin, and a hot-melt layer laminated on an opposite surface ofthe first barrier layer and including a material selected from the groupconsisting of linear low density polyethylene (LLDPE), low densitypolyethylene (LDPE), high density polyethylene (HDPE), castedpolypropylene (CPP), polyethylene, polyethylene terephthalate (PET),polypropylene (PP), ethylene vinyl acetate (EVA), epoxy resin, andphenol resin.

In this case, the heat-insulation film further may include aheat-insulation coating layer interposed between the first film layerand the first bonding layer and including glass fiber.

According to one embodiment, the heat-insulation film may have a complexheat-insulation film structure in which a second film layer including amaterial selected from the group consisting of polyethyleneterephthalate (PET), polyethylene naphthalate (PEN), and polyimide (PI)is additionally laminated on the opposite surface of the first barrierlayer through a second bonding layer, which includes a material selectedfrom the group consisting of linear low density polyethylene (LLDPE),low density polyethylene (LDPE), high density polyethylene (HDPE),casted polypropylene (CPP), polyethylene, polyethylene terephthalate,polypropylene, ethylene vinyl acetate (EVA), epoxy resin, and phenolresin, while being interposed between the first barrier layer and thehot-melt layer.

According to another embodiment, a second barrier layer may beadditionally laminated on an opposite surface of the second film layerthrough a third bonding layer, which includes a material selected fromthe group consisting of linear low density polyethylene (LLDPE), lowdensity polyethylene (LDPE), high density polyethylene (HDPE), castedpolypropylene (CPP), polyethylene, polyethylene terephthalate,polypropylene, ethylene vinyl acetate (EVA), epoxy resin, and phenolresin, while being interposed between the second film layer and thehot-melt layer.

In addition, there is provided a method of fabricating a vacuum thermalinsulator, which includes cutting a core material, arranging theheat-insulation film at upper and lower portions of the core material totransfer the heat-insulation film to a vacuum forming device, theheat-insulation film serving as an outer skin material, forming an innerpart of the vacuum forming device in a vacuum state, forming the vacuumthermal insulator by performing a thermal-fusion process for the outerskin material and the core material using a heating unit, and cutting anouter portion of the formed vacuum thermal insulator.

For example, the core material may include a material selected from thegroup consisting of ceramic paper, cerakwool, distillation silica,polyurethane foam, glass wool, aerogel, non-woven fabric, Techlon, and arockwool board.

Meanwhile, the present invention provides a vacuum thermal insulatorincluding a core material constituting a heat-insulation layer and theheat-insulation film, which serves as an outer skin material covered onan outer portion of the core material.

In this case, the core material may include a material selected from thegroup consisting of ceramic paper, cerakwool, distillation silica,polyurethane foam, glass wool, aerogel, non-woven fabric, Techlon, and arockwool board.

Advantageous Effects

As described above, the present invention suggests the heat-insulationfilm having excellent heat resistance and the vacuum thermal insulatorconfigured by surrounding the outer portion of the core material usingthe heat-insulation film.

The heat-insulation film has excellent heat resistance. Accordingly,since the heat-insulation film can be covered on the outer portion ofthe core material through the thermal-fusion process. Accordingly, theprocessing work and the forming work can be easily performed. Theforming work can be performed in the tight contact with the corematerial.

In particular, different from the related art, the heat-insulation filmis simultaneously and completely covered on the outer portion of thecore material while tightly making contact with the outer portion of thecore material, so that air or moisture may not penetrate through theheat-insulation film. Accordingly, a higher vacuum state can bemaintained. Especially, the deformation of the heat-insulation film canbe prevented even at higher humidity. Accordingly, the vacuum state canbe maintained and the heat-insulation performance can be continuouslymaintained.

In addition, the heat-insulation film can be smoothly covered on thesurface of the core material through the thermal-fusion process. Inaddition, the heat-insulation film can be prevented from being twistedat the edge region, so that the failure rate can be reduced.

DESCRIPTION OF DRAWINGS

FIG. 1 is a sectional view schematically showing the laminationstructure of a heat-insulation film according to a first embodiment ofthe present invention.

FIG. 2 is a sectional view schematically showing the laminationstructure of a heat-insulation film according to a second embodiment ofthe present invention.

FIG. 3 is a sectional view schematically showing the laminationstructure of a heat-insulation film according to a third embodiment ofthe present invention.

FIG. 4 is a sectional view schematically showing the laminationstructure of a heat-insulation film according to a fourth embodiment ofthe present invention.

FIG. 5 is a flowchart schematically showing a process of fabricating avacuum thermal insulator through a thermal-fusion process using aheat-insulation film fabricated according to the present invention.

FIG. 6 is a schematic view showing a vacuum forming device to perform athermal-fusion process in a vacuum state according to the presentinvention.

FIGS. 7 a to 7 c are sectional views schematically showing a process offabricating a vacuum thermal insulator having a structure in which aheat-insulation film according to the present invention is covered on anouter portion of the core material through the thermal-fusion process.

FIGS. 8 a to 8 e are photographs showing the states of the vacuumthermal insulator fabricated according to the present invention,respectively.

BEST MODE Mode for Invention

The present inventors make the present invention based on an idea thatit is preferred that a heat-insulation film is bonded to an outerportion of a core material through a thermal-fusion scheme of a hot meltscheme in order to solve a problem occurring in the related art.Hereinafter, the present invention will be described in more detail withreference to accompanying drawings. FIG. 1 is a sectional viewschematically showing the lamination structure of a heat-insulation filmaccording to a first embodiment of the present invention. As shown inFIG. 1, a heat-insulation film 100 according to a first embodiment ofthe present invention includes a first film layer 110 formed of polymerresin, a first bonding layer 120 bonded to one surface of the first filmlayer 110, a first barrier layer 130 laminated on one surface of thefirst bonding layer 120, and a hot-melt layer 140 attached to onesurface of the first barrier layer 130.

The heat-insulation film 100 according to the first embodiment isconfigured to employ a thermal-fusion scheme in a process of coveringthe heat-insulation film 100 on an outer portion of a core materialusing a material maintaining a basic physical property at a hightemperature, for example the temperature of 120° C. to 250° C.,preferably, 200° C. to 250° C. For example, polymer resin having a highglass transition temperature may be used for the first film layer 110,the first bonding layer 120, and the hot-melt layer 140. In detail, thefirst film layer 110, which protects a surface or the core materialbonded to an inner part of the heat-insulation film 100 from externalimpact, is formed of polymer resin having excellent impact resistance ormaintaining a physical property thereof at a high temperature. Forexample, the first film layer 110 may include polymer resin selectedfrom the group consisting of polyethylene terephthalate (PET),polyethylene naphthalate (PEN), and polyimide (PI). Preferably, thefirst film layer 110 may have the thickness in the range of 4 μm to 350μm. If the thickness of the first film layer 110 is less than a value inthe above range, the first film layer 110 may be damaged due to externalimpact or scratch. If the thickness of the first film layer 110 exceedsthe value in the above range, when a vacuum thermal insulator to bedescribed below is fabricated, a problem may occur. For example,regarding the polymer resin constituting the first film layer 110,polyethylene terephthalate (PET), such as “Skynex® NXIO(SKC)”, “Skynex®TKIO(SKC)”, “Skynex® TK20(SKC)”, or “Skynex® TK50(SKC)” and polyimide(PI) such as IF70 (SKC) may be used.

However, the present invention is not limited thereto, but the firstfilm layer 110 may include various materials.

Meanwhile, the first bonding layer 120 bonded to one surface of thefirst film layer 110 may include polymer resin selected from the groupconsisting of linear low density polyethylene (LLDPE), low densitypolyethylene (LDPE), high density polyethylene (HDPE), castedpolypropylene (CPP), polyethylene, polyethylene terephthalate (PET),polypropylene (PP), ethylene vinyl acetate (EVA), epoxy resin such asmodified epoxy resin, and phenol resin such as modified phenol resin.The first bonding layer 120 may be bonded to the first film layer 110 atthe thickness of 1 μm to 100 μm.

Meanwhile, the first barrier layer 130 laminated on the first bondinglayer 120 in opposition to the first film layer 110 serves as a gasbarrier layer. The first barrier layer 130 may include an aluminum foil,preferably an inorganic material such as aluminum, alumina, or silicon.Preferably, the first barrier layer 130 is laminated at the thickness of5 μm to 100 μm.

Meanwhile, the hot-melt layer 140, which is laminated on one surface ofthe first barrier layer 130 to tightly make contact with the outersurface of the core material in the process of covering the outerportion of the core material with the heat-insulation film 100, mayinclude polymer resin having an excellent sealing property. For example,the hot-melt layer 140 include polymer resin selected from the groupconsisting of linear low density polyethylene (LLDPE), low densitypolyethylene (LDPE), high density polyethylene (HDPE), castedpolypropylene (CPP), polyethylene, polyethylene terephthalate (PET),polypropylene (PP), ethylene vinyl acetate (EVA), epoxy resin, andphenol resin. For example, the hot-melt layer 140 may be laminated at athickness in the range of 1 μm to 100 μm, preferably the thickness inthe range of 3 μm to 100 μm. If the thickness of the hot-melt layer 140is less than a value in the above range, the hot-melt layer 140 may nottightly make contact with the core material. If the thickness of thehot-melt layer 140 exceeds the value in the above range, the durabilityof a vacuum thermal insulator finally fabricated may be degraded. In thecase of a conventional heat-insulation film used for the vacuum thermalinsulator, a high-frequency bonding scheme is employed. Theheat-insulation film according to the present invention including theheat-insulation film 100 according to the first embodiment forms thehot-melt layer 140, so that the heat-insulation film can be stably andrapidly covered on the outer portion of the core material.

According to the first embodiment of the present invention, the firstbonding layer 120 and the hot-melt layer 140 may include polymer resinselected from the group consisting of linear low density polyethylene(LLDPE), low density polyethylene (LDPE), high density polyethylene(HDPE), casted polypropylene (CPP), polyethylene (PE), polyethylene,polyethylene terephthalate (PET), polypropylene (PP), ethylene vinylacetate (EVA), epoxy resin, and phenol resin representing an excellentphysical property such as impact strength and flexibility. Therefore,not only can the heat resistance of the heat-insulation film 100 beimproved, but also the durability of the vacuum thermal insulatorproduced by covering the heat-insulation film 100 onto the outer portionof the core material through the thermal-fusion process can be improved,thereby preventing the heat-insulation film 100 from being damaged byexternal impact.

The heat-insulation film 100 according to the first embodiment can becovered on the outer portion of the core material while maintaining thebasic physical property thereof even through the high-temperaturethermal fusing forming process, so that the heat-insulation film 100 canbe utilized for the vacuum thermal insulator. However, in order toaccomplish a more excellent insulating effect, components may be furtherprovided. FIG. 2 is a sectional view schematically showing thelamination structure of a heat-insulation film according to the secondembodiment of the present invention. In the structure of aheat-insulation film 200 shown in FIG. 2, since a first film layer 210,a first bonding layer 220, a first barrier layer 230, and a hot-meltlayer 240 are the same as those described with reference to FIG. 1, thedetails thereof will be omitted. The heat-insulation film 200 shown inFIG. 2 further includes a heat-insulation coating layer 250 interposedbetween the first film layer 210 and the first bonding layer 220 andformed of a heat-insulation material such as glass fiber to moremaximize the heat-insulation effect. The heat-insulation coating layer250 may have various thicknesses sufficient to provide a heat-insulationeffect to the heat-insulation film 200. For example, the heat-insulationcoating layer 250 may be formed at the thickness of 1 μm to 100 μm.

Meanwhile, although FIGS. 1 and 2 show that a heat-insulation filmincluding one film layer, a complex heat-insulation film including atleast two film layers if necessary may be taken into consideration. FIG.3 is a sectional view schematically showing the lamination structure ofthe heat-insulation film according to a third embodiment. In thestructure of a heat-insulation film 300 shown in FIG. 3, since a firstfilm layer 310, a first bonding layer 320, a first barrier layer 330,and a hot-melt layer 340 are the same as those described in the firstembodiment, the details thereof will be omitted.

In the heat-insulation film 300 according to the third embodiment, asecond film layer 312 is interposed between the first barrier layer 330and the hot-melt layer 340 through a second bonding layer 322. In thiscase, the second bonding layer 322 may include linear low densitypolyethylene (LLDPE), low density polyethylene (LDPE), high densitypolyethylene (HDPE), casted polypropylene (CPP), polyethylene,polyethylene terephthalate (PET), polypropylene (PP), ethylene vinylacetate (EVA), epoxy resin, or phenol resin. The second bonding layer322 may be provided at a thickness substantially equal to that of thefirst bonding layer 320 and interposed between the first barrier layer330 and the second film layer 312. Meanwhile, the second film layer 312may include a material selected from the group consisting of PET, PEN,and PI. For example, the second film layer 312 may be laminated at thethickness in the range of 4 μm to 350 μm.

According to the third embodiment described above, two film layers areprovided to maximize the heat-insulation effect. The present inventionis not limited to a complex heat-insulation film including two filmlayers, but the complex insulation film may include at least three filmlayers. In addition, similarly to the second embodiment, aheat-insulation coating layer formed of glass fiber may be additionallyinterposed between the first film layer 310 and the first bonding layer320 and/or between the second film layer 312 and the second bondinglayer 322. Meanwhile, a complex insulating film having a multi-layerstructure including at least two barrier layers may be taken intoconsideration in addition to the formation of at least two polymer resinfilm layers. FIG. 4 is a sectional view schematically showing thelamination structure of a heat-insulation film according to the fourthembodiment of the present invention. When comparing with the thirdembodiment, since a first film layer 410, a first bonding layer 420, afirst barrier layer 430, a second bonding layer 422, a second film layer412, and a hot-melt layer 440 have the same structure as that of thethird embodiment, the details thereof will be omitted. In a complexheat-insulation film 400 having the multi-structure according to thepresent embodiment, a second barrier layer 432 is additionallyinterposed between the second film layer 412 and the hot-melt layer 440through the third bonding layer 424. In this case, the third bondinglayer 424 includes a material selected from the group consisting oflinear low density polyethylene (LLDPE), low density polyethylene(LDPE), high density polyethylene (HDPE), casted polypropylene (CPP),polyethylene, polyethylene terephthalate (PET), polypropylene (PP),ethylene vinyl acetate (EVA), epoxy resin, and phenol resin and isinterposed between the second film layer 412 and the second barrierlayer 432. The third bonding layer 424 may be interposed at thethickness equal to those of the first bonding layer 420 and the secondbonding layer 422. Meanwhile, the second barrier layer 432 may serve asa gas-barrier layer similarly to the first barrier layer 430, and may belaminated at the thickness in the range of 5 μm to 100 μm.

According to the fourth embodiment described above, two film layers areprovided to maximize the heat-insulation effect. The present inventionis not limited to a complex heat-insulation film including two filmlayers, but the complex insulation film may include at least three filmlayers including polymer resin and at least three barrier layers. Inaddition, similarly to the second embodiment, a heat-insulation coatinglayer formed of glass fiber may be interposed between the first filmlayer 410 and the first bonding layer 420 and/or between the second filmlayer 412 and the second bonding layer 422.

As described in the third and fourth embodiments, if a complexheat-insulation film having a multi-layer structure in which at leasttwo film layers and/or at least two barrier layers are laminated isused, excellent heat resistance can be acquired, and tensile force andthe heat-insulation effect can be enhanced to maximize flame resistance.Accordingly, the complex heat-insulation film can be utilized forheat-insulation necessary for a special application field, for example apipe and a turbine of nuclear power generation, hydroelectric powergeneration, and thermoelectric power generation, and other industrialfields.

Subsequently, a process of fabricating the vacuum thermal insulator bycovering the heat-insulation film onto the outer portion of the corematerial according to the present invention will be described. Althoughdescription will be made regarding the heat-insulation film 100according to the first embodiment among the above-describedheat-insulation films, other heat-insulation films may be covered ontothe outer portion of the core material through the same process. FIG. 5is a flowchart schematically showing a process of fabricating the vacuumthermal insulator through the thermal-fusion process using theheat-insulation film fabricated according to the present invention. FIG.6 is a schematic view showing a vacuum forming device to perform thethermal-fusion process in a vacuum state according to the presentinvention. FIGS. 7 a to 7 c are sectional views schematically showing aprocess of fabricating the vacuum thermal insulator having a structurein which the heat-insulation film according to the present invention iscovered on an outer portion of the core material through thethermal-fusion process. First, a core material is cut in a desirablesize using a cutting unit, and a cutting surface is primarily machinedso that the cutting surface is smoothly made (S510). The primarilymachined core material 500 is introduced into a drying furnace to drythe core material 500, so that moisture can be completely removed fromthe core material 500 (S520). The cutting unit to cut the core material500 in the desirable size may include a typical saw blade or water-jetusing water.

The core material 500, which may be used in the present invention, maybe a certain core material used in fabricating a conventional vacuumthermal insulator. For example, the core material 500 may include oneselected from the group consisting of ceramic paper, cerakwool,distillation silica, polyurethane foam, glass wool, aerogel, non-wovenfabric, Techlon, and a rockwool board. Preferably, if nonflammablematerials, such as ceramic paper, cerakwool, aerogel, Techlon, and arockwool board, are used, safety from fire can be ensured, and thematerial includes ingredients that are not harmful to the human body tosatisfy the eco-friendly trend.

The core material 500 subject to the drying process and heat-insulationfilms 100A and 100B, which are additionally prepared, are transferredinto a vacuum forming device 600 through a transfer unit such as aconveyer belt in the state that the above materials are arranged above aforming die (forming tray 610) (S530). As shown in FIG. 6, after thefirst heat-insulation film 100A is first provided on the forming die610, and the core material 500 is provided on the first heat-insulationfilm 100A, the second heat-insulation film 100B is provided on the corematerial 500. In this state, the materials may be transferred into thevacuum forming device 600. In this case, the heat-insulation films 100Aand 100B may be covered on the outer portion of the core material 500through hot-melt layers of the heat-insulation films 100A and 100B. Tothis end, as shown in FIG. 7 a, the first heat-insulation film 100A isprovided in such a manner that a first hot-melt layer 140A is positionedon the first heat-insulation film 100A provided under the core material500, and the second heat-insulation film 100B is provided in such amanner that a second hot-melt layer 140B is positioned under the secondheat-insulation film 100B.

In the process of providing the heat-insulation films 100A and 100B andthe core material 500, the first and second heat-insulation films 100Aand 100B extend in a longitudinal direction with a length longer thanthat of the core material 500. Accordingly, in the thermal-fusionprocess, an outer lateral side of the core material 500 can besurrounded by the first and second heat-insulation films 100A and 100Bin addition to the top surface and the bottom surface of the corematerial 500. For example, the first heat-insulation film 100A isprovided inside a forming frame 612 protruding upward from the edge ofthe forming die 610, and the edge of the second heat-insulation film100B may be supported by the forming frame 612.

In the above arrangement state, an inner part of the vacuum formingdevice 600 having the core material 500 and the heat-insulation films100A and 100B arranged therein is made in a vacuum state using a vacuumpump 620 coupled to the vacuum forming device 600 (S540). In order toform a vacuum heat-insulation material, the vacuum state may be about10⁻⁴ Torr or less (about 0.01 Pa or less). The vacuum pump 620 to makethe high-vacuum state may include a rotary pump, a booster pump, and adiffusion pump. Thereafter, heat is applied to the inner part of thevacuum forming device 600 using a heating unit 630 provided in thevacuum forming device 600 to perform a thermal-fusion process so thatthe heat-insulation films 100A and 100B are covered on the outer portionof the core material 500 (S550). The temperature of the heating unit 630may be adjusted to the temperature in the range of 180° C. to 250° C.The heat-insulation films 100A and 100B are covered on the outer portionof the core material 500 through the thermal-fusion process by heatsupplied from the heating unit 630. In other words, as shown in FIG. 7b, the hot-melt layers 140A and 140B tightly making contact with thecore material 500 in the heat-insulation films 140A and 140B providedunder and on the core material 500, respectively, are contracted andmelt so that the top surface and the bottom surface of the core material500 and both lateral sides of the core material 500 are covered with theheat-insulation films 100A and 100B, thereby forming the vacuum thermalinsulator. For example, the heating unit 630 may include a hot wire, butthe present invention is not limited thereto.

A conventional heat-insulation film used for a vacuum thermal insulatoris covered on the outer portion of the core material through ahigh-frequency scheme after vacuum, so that a problem may occur in theadhesive strength with the core material. However, according to thepresent invention, since the heat-insulation film is bonded to the corematerial through the thermal-fusion process, the adhesive strength andthe adhesive maintain capability can be improved, so that asignificantly excellent vacuum state can be maintained. In addition,excellent performance can be maintained in preventing a film from beingdeformed by moisture.

The vacuum thermal insulator primarily processed after thethermal-fusion process is aged for a predetermined time until the vacuumthermal insulator is cooled so that the heat-insulation films 100A and100B are completely bonded to the core material 500 (S570). The formedvacuum thermal insulator is withdrawn out of the vacuum forming device600 and a forming frame 620. Thereafter, an outer edge of the vacuumthermal insulator is cut using a cutting unit such as a blade.Accordingly, as shown in FIG. 7 c, the vacuum thermal insulator 700,which is formed by covering the heat-insulation films 100A and 100B onthe outer portion of the core material 500, may be completed. Whenforming a vacuum thermal insulator according to a conventional scheme,in the process of covering and cutting a heat-insulation film covered onthe outer portion of the core material, especially the process offorming an edge portion of a produce, the film may be twisted so thatthe failure rate may be increased. According to the present inventionemploying the thermal-fusion scheme, when the heat-insulation film iscut, the cutting surface of the heat-insulation film can be smoothlyprocessed, and the twisting of the edge portion is removed, so that thefailure rate may be significantly reduced. Vacuum thermal insulatorssubject to the final cutting are packaged according to sizes in a box(S580), thereby completing the fabrication process of the vacuuminsulator.

Although the present invention will be described below using exemplarembodiments, the preset invention is not limited thereto.

EMBODIMENT 1 Fabrication of Heat-Insulation Film

An epoxy resin hot-melt adhesive agent was applied on a bottom surfaceof a first film layer formed at the thickness of 25 μm and formed ofpolyethylene terephthalate (SKC, Skynex®, or NX10) by a laminatingmachine, thereby forming a first adhesive layer having the thickness of5 μm. A first barrier layer including an aluminum foil was laminated atthe thickness of 15 μm on the bottom surface of the first film layer bythe laminating machine, and a modified epoxy resin hot-melt adhesive wasapplied at the thickness of 20 μm on the first barrier layer.

EMBODIMENT 2 Fabrication of Heat-Insulation Film

A heat-insulation film according to the second embodiment was fabricatedby repeating the procedure of the first embodiment except that a glassfiber having the thickness of 20 μm was interposed between a first filmlayer and a first bonding layer.

EMBODIMENT 3 Fabrication of Heat-Insulation Film

A heat-insulation film according to the third embodiment was fabricatedby repeating the procedure of the first embodiment except that an epoxyresin hot-melt adhesive was applied between a first barrier layer and aholt-melt layer to form a second adhesive layer having the thickness of15 μm, and a second film layer formed at the thickness of 100 μm andformed of polyethylene terephthalate (SKC, Skynex®, or NX10) wasadditionally formed.

EMBODIMENT 4 Fabrication of Heat-Insulation Film

A heat-insulation film according to the fourth embodiment was fabricatedby repeating the procedure of the third embodiment except that an epoxyresin hot-melt adhesive was applied between a second barrier layer and aholt-melt layer to form a third adhesive layer having the thickness of15 μm, and a second barrier layer having the thickness of 30 μm wasfurther laminated.

EMBODIMENT 5 Fabrication of Heat-Insulation Film

The heat-insulation films fabricated according to the first to fourthembodiments described above were used as outer skin materials, andceramic paper was used as a core material to fabricate the vacuumthermal insulator. The core material is cut in the size of 270 mm×270mm, and the heat-insulation film and the core material were provided ina forming frame and set in a vacuum forming device. After the internalpressure of the vacuum forming device was adjusted to 10⁻⁴ torr, thetemperature of the hot wire and the heating time were adjusted tovarious values, thereby performing the thermal-fusion process. After thethermal-fusion process was completed and the formed vacuum thermalinsulator was aged, the bonding state between the heat-insulation filmand the core material, the surface state, and the thickness variationwere measured. The following table 1 shows the thermal-fusiontemperature and the heating time of the vacuum thermal insulator, andthe following table 2 shows a physical property test result.

TABLE 1 Temperature Transmission Heating Core Embodiment of hot wiretemperature time (Sec) material 3 193 105 3 Ceramic paper 1 193 105 3Ceramic paper 2 193 105 3 Ceramic paper 3 193 105 3 Ceramic paper 4 193105 3 Ceramic paper

TABLE 2 Bonding state Surface state Thickness change Front Rear FrontRear Before After Embodiment surface surface surface surface formingforming 3 ◯ ◯ Good Good 5Tx4   9T 1 ◯ ◯ Good Good 5Tx2 4.5T 2 ◯ ◯ GoodGood 5Tx2 4.5T 3 ◯ ◯ Good Good 5Tx2 4.5T 4 ◯ ◯ Good Good 5Tx2 4.5T

In addition, FIGS. 8 a to 8 e show the shapes of the vacuum thermalinsulators fabricated according to the present embodiments,respectively. The core material was excellently bonded to theheat-insulation film, and the corner and the edge region were smoothlycut.

1. A heat-insulation film comprising: a first film layer comprising amaterial selected from the group consisting of polyethyleneterephthalate (PET), polyethylene naphthalate (PEN), and polyimide (PI);a first barrier layer laminated on one surface of the first film layerthrough a first bonding layer comprising a material selected from thegroup consisting of linear low density polyethylene (LLDPE), low densitypolyethylene (LDPE), high density polyethylene (HDPE), castedpolypropylene (CPP), polyethylene, polyethylene terephthalate (PET),polypropylene (PP), ethylene vinyl acetate (EVA), epoxy resin, andphenol resin; and a hot-melt layer laminated on an opposite surface ofthe first barrier layer and comprising a material selected from thegroup consisting of linear low density polyethylene (LLDPE), low densitypolyethylene (LDPE), high density polyethylene (HDPE), castedpolypropylene (CPP), polyethylene, polyethylene terephthalate (PET),polypropylene (PP), ethylene vinyl acetate (EVA), epoxy resin, andphenol resin.
 2. The heat-insulation film of claim 1, further comprisinga heat-insulation coating layer interposed between the first film layerand the first bonding layer and comprising glass fiber.
 3. Theheat-insulation film of claim 1, further comprising a second film layercomprising a material selected from the group consisting of polyethyleneterephthalate (PET), polyethylene naphthalate (PEN), and polyimide (PI)and additionally laminated on the opposite surface of the first barrierlayer through a second bonding layer, which comprises a materialselected from the group consisting of linear low density polyethylene(LLDPE), low density polyethylene (LDPE), high density polyethylene(HDPE), casted polypropylene (CPP), polyethylene, polyethyleneterephthalate, polypropylene, ethylene vinyl acetate (EVA), epoxy resin,and phenol resin, while being interposed between the first barrier layerand the hot-melt layer.
 4. The heat-insulation film of claim 3, furthercomprising a second barrier layer additionally laminated on an oppositesurface of the second film layer through a third bonding layer, whichcomprises a material selected from the group consisting of linear lowdensity polyethylene (LLDPE), low density polyethylene (LDPE), highdensity polyethylene (HDPE), casted polypropylene (CPP), polyethylene,polyethylene terephthalate, polypropylene, ethylene vinyl acetate (EVA),epoxy resin, and phenol resin, while being interposed between the secondfilm layer and the hot-melt layer.
 5. A method of fabricating a vacuumthermal insulator, the method comprising: cutting a core material;arranging a heat-insulation film according to claim 1 at upper and lowerportions of the core material to transfer the heat-insulation film to avacuum forming device, the heat-insulation film serving as an outer skinmaterial; forming an inner part of the vacuum forming device in a vacuumstate; forming the vacuum thermal insulator by performing athermal-fusion process for the outer skin material and the core materialusing a heating unit; and cutting an outer portion of the formed vacuumthermal insulator.
 6. The method of claim 5, wherein the core materialcomprises a material selected from the group consisting of ceramicpaper, cerakwool, distillation silica, polyurethane foam, glass wool,aerogel, non-woven fabric, Techlon, and a rockwool board.
 7. A vacuumthermal insulator comprising a core material constituting aheat-insulation layer and a heat-insulation film according to claim 1,which serves as an outer skin material covered on an outer portion ofthe core material.
 8. The vacuum thermal insulator of claim 7, whereinthe core material comprises a material selected from the groupconsisting of ceramic paper, cerakwool, distillation silica,polyurethane foam, glass wool, aerogel, non-woven fabric, Techlon, and arockwool board.
 9. A vacuum thermal insulator comprising a core materialconstituting a heat-insulation layer and a heat-insulation filmaccording to claim 2, which serves as an outer skin material covered onan outer portion of the core material.
 10. A vacuum thermal insulatorcomprising a core material constituting a heat-insulation layer and aheat-insulation film according to claim 3, which serves as an outer skinmaterial covered on an outer portion of the core material.
 11. A vacuumthermal insulator comprising a core material constituting aheat-insulation layer and a heat-insulation film according to claim 4,which serves as an outer skin material covered on an outer portion ofthe core material.